Eddy Current Method, phase-sensitive

Eddy current test method (phase sensitive) according to the standard ISO 21968.

Schematic diagram of the phase sensitive eddy current method. The penetration depth of the magnetic field depends on the used frequency and the electrical conductivity of the materials.

Functional principle

Contact method: The excitation current generates a high-frequency magnetic field, which induces eddy currents in the material (coating or base material). The different formation of the eddy currents in the coating material and the base material is used for the coating thickness measurement. The phase shift Phi between the excitation current and the measurement signal is converted to a coating thickness value by using the characteristic probe output function, i.e., the functional correlation between the measurement signal and the coating thickness. In a certain range, which is determined by the probe, the reading is not dependent on the distance between the probe and the coating surface.